[In the authors' words, "A weak
pun on Multics"; very early on it was `UNICS'] (also `UNIX') An
interactive time-sharing system invented in 1969 by Ken Thompson
after Bell Labs left the Multics project, originally so he could
play games on his scavenged PDP-7. Dennis Ritchie, the inventor of
C, is considered a co-author of the system. The turning point in
Unix's history came when it was reimplemented almost entirely in C
during 1972-1974, making it the first source-portable OS. Unix
subsequently underwent mutations and expansions at the hands of
many different people, resulting in a uniquely flexible and
developer-friendly environment. By 1991, Unix had become the most
widely used multiuser general-purpose operating system in the world
- and since 1996 the variant called Linux has been at the
cutting edge of the open source movement. Many people
consider the success of Unix the most important victory yet of
hackerdom over industry opposition (but see Unix weenie and
Unix conspiracy for an opposing point of view). See
Version 7, BSD, Linux.

Some people are confused over whether this word is appropriately
`UNIX' or `Unix'; both forms are common, and used interchangeably.
Dennis Ritchie says that the `UNIX' spelling originally happened in
CACM's 1974 paper "The UNIX Time-Sharing System" because "we
had a new typesetter and troff had just been invented and we
were intoxicated by being able to produce small caps." Later, dmr
tried to get the spelling changed to `Unix' in a couple of Bell
Labs papers, on the grounds that the word is not acronymic. He
failed, and eventually (his words) "wimped out" on the issue.
So, while the trademark today is `UNIX', both capitalizations are
grounded in ancient usage; the Jargon File uses `Unix' in deference
to dmr's wishes.